During its practical use as a mat and its periodic wash and drying processing in industrial laundries, the primary physical damage that is encountered by a rubber backed, press molded mat is tearing at both the edges and the longitudinal borders. Such washing processes are effectuated in well known rotary washings machines which apply appreciable stress and force on the subject mats. The same holds true during the industrial rotary drying procedures, too. Thus, such mats must possess suitable flexibility to withstand the rigors of such industrial laundering. Such flexibility, however, may facilitate damage to the mats due to the aforementioned tearing during industrial laundering. Thus, suitable reinforcement is required to prevent tearing during the stress of such industrial laundry applications. This tearing typically occurs at the edge of the piled textile covering on the mat. The edge of the piled textile covering is referred to as the border interface on the mats. Previous attempts to alleviate this problem have basically only included placing reinforcement strips around a rubber mat backing sheet by hand, subjecting the sheet to a vulcanization step, and cutting, again, by hand, the residual excess border strips from the mat. Such a process inevitably results in non-uniform reinforcement and a general lack of aesthetics for the majority of mats produced with hand-laid reinforcement strips. A more uniform manner of producing more aesthetically and better performing mats is thus necessary.
The art includes a number of configurations and features for various floor mats. Some patents which are believed to be illustrative of known mats include U.S. Pat. No. 2,254,210 to Cunnington, issued Sep. 2, 1941; U.S. Pat. No. 3,306,808 to Thompson, et al. issued Feb. 28, 1967; U.S. Pat. No. 3,953,631 to Gordon issued Apr. 27, 1976; U.S. Pat. No. 4,741,065 to Parkins issued May 3, 1988; U.S. Pat. No. 4,886,692 to Kerr et al. issued Dec. 12, 1989; U.S. Pat. No. 5,227,214 to Kerr et al. issued Jul. 13, 1993; U.S. Pat. No. 5,240,530 to Fink issued Aug. 31, 1993; U.S. Pat. No. 5,305,565 to Nagahama et al. issued Apr. 26, 1994; and U.S. Pat. No. 5,350,478 to Bojstrup et al. issued Sep. 27, 1994; all of which are incorporated herein by reference.
The construction of mats using rubber backing sheets which nonetheless provide good tear resistance has generally been limited to the following methods:
1. The formulation of high tear and high tensile strength rubber in a uniform thick sheet (typically 59-65 mils) which extends beyond the dimensions of the pile covering; and PA1 2. The construction of a five piece rubber mat backing which constitutes a uniform thick (typically 40-45 mils) sheet which serves as the body piece and which is smaller in dimensions than the textile covering and four strips of rubber (typically twice as thick as the body piece) which are manually placed beneath the textile edges of the mat. PA1 (a) optionally, simultaneously mating first and second strips of perforated carboxylated rubber to the longitudinal borders of a rubber sheet; PA1 (b) optionally, joining said first and second strips of perforated carboxylated rubber to said rubber sheet by means of pressure applied by a plurality contacting rollers while step "a" is ongoing; PA1 (c) optionally, mating a third strip of perforated carboxylated rubber simultaneously to the leading edge of said rubber sheet; PA1 (d) optionally, joining said third strip of perforated carboxylated rubber to said leading edge of said rubber sheet by means of pressure applied by a contacting roller; PA1 (e) mating a fourth strip of perforated carboxylated rubber simultaneously to the tailing edge of said rubber sheet; PA1 (f) joining said fourth strip of perforated carboxylated rubber to said tailing edge of said rubber sheet by means of pressure applied by a contacting roller; PA1 (g) delivering said rubber sheet to an in-line cutter following either of joining steps "d" or "f"; PA1 (h) cutting said rubber sheet to a designed length; PA1 (i) placing a pile fabric on said rubber sheet to form a pile composite; and PA1 (j) vulcanizing said pile composite to form a unitary structure.
In the vulcanization of a rubber backed mat with a textile covering, the edges of the textile tend to embed deeper within the rubber as compared to other portions of the mat. This embedding is believed to result from the rubber flow at the border of the textile covering as pressure is applied from an inflatable diaphragm and the rubber undergoes reduced viscosity due to the application of heat. As will be appreciated, the unrestrained rubber movement in the border allows the longitudinal edges of the textile to move deeper into the rubber backing thus creating a thinning of the rubber at the border interface. As indicated previously, it is this thinner interface which is susceptible to tears during the mat's use and industrial laundry processing. Such industrial laundry processing entails the introduction of these rubber-backed mats into automated washing machines and, subsequently, rotating dryers.
In attempts to alleviate such tearing of the rubber mat, the industry has relied on the two previously described methods of production. Method 1 has an advantage of minimum labor requirements and cycle times but requires the use of a relatively thick rubber backing which tends to make the mat heavier and to increase raw material costs. Method 2 permits the use of a thinner rubber backing which is desirable for laundry processing. However, the five piece construction has the drawback of requiring additional labor to carry out placement of the edge portions and longer vulcanization times to cure the thicker rubber edges compared to the thinner body section beneath the textile covering.
It has been suggested that built up edge strips may be co-calendared with the rubber backing sheet as the backing sheet is produced. Thereafter, the backing sheet material (including the built up edges) may be delivered in roll form to the mat manufacturing location. While such a co-calendaring operation is effective in producing rubber sheets with enhanced edge thickness, it has been found that there is some difficulty in the handling of rolls of such co-calendared material since the edges have a thickness several mils thicker than the interior. Due to this difference in thickness, a roll of the material takes on a substantially dog-bone profile wherein the outer edges of the roll are of greater diameter than the center. As will be appreciated, this disparity in diameter increases dramatically with any increase in the outer edge thickness. Moreover, a significant disparity in roll diameter may give rise to difficulty in later processing steps as the backing material is drawn off the roll for production of the mat. Specifically, with a significant difference in diameter along the length of the roll it may be difficult to maintain a constant feed of the backing material without the occurrence of folds or wrinkles along the surface of the material.
In light of the above, it will be appreciated that there is a need for a process and apparatus to apply efficiently a tear-resistant border to a rubber backing sheet for a dust control mat as an in-line operation during the assembly of the mat. The present invention thus represents a useful advancement over prior practice.